I wanted to install # on the tablet, but it was no longer on # whaat.

Turns out it's because it's old and signed with md5. All such apps have been moved to the F-Droid Archive. Luckily the Archive is trivial to find and activate, just go to Settings->Repositories and there's a convenient switch to flip.

Of course, in this case I don't believe it's a big problem, Liquid Wars doesn't have permissions for anything except network access, but for other apps you might want to think twice before you install something considered insecure.

https://forum.f-droid.org/t/many-old-unmaintained-apps-have-been-archived/670/14